Serological Evidence of Ebola Virus Infection in Indonesian Orangutans

Abstract

Ebola virus (EBOV) and Marburg virus (MARV) belong to the family Filoviridae and cause severe hemorrhagic fever in humans and nonhuman primates. Despite the discovery of EBOV (Reston virus) in nonhuman primates and domestic pigs in the Philippines and the serological evidence for its infection of humans and fruit bats, information on the reservoirs and potential amplifying hosts for filoviruses in Asia is lacking. In this study, serum samples collected from 353 healthy Bornean orangutans (Pongo pygmaeus) in Kalimantan Island, Indonesia, during the period from December 2005 to December 2006 were screened for filovirus-specific IgG antibodies using a highly sensitive enzyme-linked immunosorbent assay (ELISA) with recombinant viral surface glycoprotein (GP) antigens derived from multiple species of filoviruses (5 EBOV and 1 MARV species). Here we show that 18.4% (65/353) and 1.7% (6/353) of the samples were seropositive for EBOV and MARV, respectively, with little cross-reactivity among EBOV and MARV antigens. In these positive samples, IgG antibodies to viral internal proteins were also detected by immunoblotting. Interestingly, while the specificity for Reston virus, which has been recognized as an Asian filovirus, was the highest in only 1.4% (5/353) of the serum samples, the majority of EBOV-positive sera showed specificity to Zaire, Sudan, Cote d’Ivoire, or Bundibugyo viruses, all of which have been found so far only in Africa. These results suggest the existence of multiple species of filoviruses or unknown filovirus-related viruses in Indonesia, some of which are serologically similar to African EBOVs, and transmission of the viruses from yet unidentified reservoir hosts into the orangutan populations. Our findings point to the need for risk assessment and continued surveillance of filovirus infection of human and nonhuman primates, as well as wild and domestic animals, in Asia.

The serology of Ebolavirus – a wider geographical range, a wider genus of viruses or a wider range of virulence?

“…It is known that apes are susceptible to EVD (Walsh et al, 2003) and also have signals of seropositivity (Becker et al, 1992;Johnson et al, 1981aJohnson et al, , 1982Leroy et al, 2004a, b;Nidom et al, 2012;Rouquet et al, 2005) but their status seems to be more similar to that of humans as occasional victims of epidemics, rather than to represent a reservoir population. Likewise, surveys of other mammals have shown seropositivity in domestic animals (Allela et al, 2005;Stansfield et al, 1982) and limited evidence of virus genomes (Morvan et al, 1999) or disease (Leroy et al, 2004;Rouquet et al, 2005) in small mammals.…”

Neglected filoviruses

“…IgG antibodies against BDBV glycoprotein (GP 1,2 ) antigen were detected by ELISA and western blot in 9/353 (2.6%) of orangutans (Pongo pygmaeus) sampled on Kalimantan Island, Indonesia, in 2006. BDBV-specific IgM could not be detected (Nidom et al 2012). These results may suggest that the BDBV distribution is not restricted to Eastern Africa.…”

“…Whereas MARV and RAVV subclinically infect bats in nature, and data for EBOV-bat associations are suggestive (Wahl-Jensen et al 2013), TAFV does not replicate in Egyptian rousette bats . No clues have been found in regard to TAFV ecology other than possibly TAFVspecific antibodies in Indonesian orangutans (Nidom et al 2012).…”

Ebola Virus ? A Global Threat

“…20,21 Since the time of first recovery, with the exception of a few accidental laboratory infections, Ebola outbreaks have been mostly concentrated in remote areas of sub-Saharan Africa, but evidence of Ebola infection of swine in the Philippines, the presence of antibodies among orangutans in Indonesia and bats in China indicates that Ebola virus may be more widespread than previously thought. [22][23][24] The frequency of recognized outbreaks has been increasing since 1990. 25 16 The virus has caused more than 20 outbreaks since its identification.…”